1. Field of the Invention
The present invention relates to a method of recovering a cleaning agent containing copper oxide as a component thereof, a cleaning agent containing basic copper carbonate as a component thereof, a cleaning agent containing copper hydroxide as a component thereof, or a cleaning agent containing copper oxide and manganese oxide as components thereof. More particularly, the invention relates to a method of recovering a copper component and/or a manganese component from a cleaning agent that has been used for removing a phosphine or a silane gas contained in a discharge gas from a semiconductor production step or a similar step.
2. Background Art
In the production steps for silicon semiconductors, compound semiconductors, etc., phosphines and hydrides (gaseous form) such as silane and disilane are employed as source gas or doping gas. Dichlorosilane is used as a source for forming silicon nitride (Si3N4) film on a semiconductor substrate such as a silicon wafer. These gases are highly harmful, and adversely affect the human body and environment if discharged to the atmosphere without any treatment. Therefore, the gases which contain these compounds and have been used in the semiconductor production steps must be cleaned prior to discharge to the atmosphere. In order to perform cleaning, there have conventionally been developed cleaning agents for harmful gases containing as a harmful component a phosphine, a silane, a disilane, or a dichlorosilane gas.
Regarding a method of cleaning a harmful gas containing a phosphine or a silane gas, the present applicant has developed a number of cleaning methods employing a cleaning agent containing copper oxide, or copper oxide and manganese oxide. According to one such cleaning method, a harmful gas containing a hydride gas such as phosphine is cleaned through contact with a cleaning agent formed of cupric oxide and an oxide of silicon and/or aluminum (Japanese Patent Application Laid-Open (kokai) No. 61-129026). Japanese Patent Application Laid-Open (kokai) Nos. 62-286521 to -286525 disclose methods of cleaning a similar harmful gas through contact with a cleaning agent formed of cupric oxide and an oxide of titanium, zirconium, lanthanum, iron, cobalt, nickel, tin, lead, antimony, bismuth, vanadium, molybdenum, tungsten, niobium, or tantalum.
Japanese Patent Application Laid-Open (kokai) No. 1-254230 discloses a method of cleaning a harmful gas containing arsine, silane, etc. by bringing the gas into contact with a cleaning agent formed of a composition containing manganese dioxide, copper oxide, and cobalt oxide serving as predominant components and a silver compound. Japanese Patent Application Laid-Open (kokai) No. 6-154535 discloses a method of cleaning a similar gas through contact with a cleaning agent formed of a composition containing manganese dioxide and copper oxide serving as predominant components and a potassium component, onto which composition a silver compound is adsorbed.
Cleaning agents containing other copper compounds include a gas treatment agent for treating a discharge gas containing a Group V inorganic compound discharged from a production step for a Group III-V compound semiconductor thin film, which agent comprises a copper compound such as basic copper carbonate (disclosed in Japanese Patent Application Laid-Open (kokai) No. 8-59391); a gas treatment agent for treating a discharge gas containing a Group V organic compound and a Group V inorganic compound discharged from production step for a Group III-V compound semiconductor thin film, which agent is prepared by mixing basic copper carbonate and potassium permanganate with anatase titanium oxide microparticles (disclosed in Japanese Patent Application Laid-Open (kokai) No. 8-155258); and a solid removing agent for removing, in a dry process, harmful components contained in a discharge gas such as volatile inorganic hydrides and halides, which agent contains crystalline cupric hydroxide as a predominant reaction component (disclosed in Japanese Patent Application Laid-Open (kokai) No. 6-319945).
Concerning copper compounds, manganese compounds, etc. which serve as components of the aforementioned cleaning agents, those assuming the form of uniform microparticles and having a high BET specific surface area have heretofore been developed. Methods of producing copper oxide of such a type are known; for example, Japanese Patent Application Laid-Open (kokai) No. 2-145422 discloses a method of preparing copper oxide microparticles of such a type comprising adding a neutralizing agent formed of an ammonium salt to a high-purity copper nitrate solution, to thereby form microparticles; and washing, drying, and calcining the thus-formed microparticles. Methods of producing manganese dioxide of such a type include a method comprising mixing a dilute aqueous solution of potassium permanganate, a dilute aqueous solution of manganese sulfate, and concentrated sulfuric acid by stirring under heating so as to form precipitates, and washing and drying the precipitates, to thereby prepare manganese dioxide of large specific surface area. In recent years, through improvement in the shape of copper oxide, manganese oxide, etc. which serve as components of a cleaning agent in an attempt to obtain excellent characteristics as well as through development of compositions of the cleaning agent as described above, cleaning agents of more excellent cleaning power (i.e., performance in cleaning a harmful component per unit amount of cleaning agent) have been produced.
After the aforementioned cleaning agents containing copper oxide as a component thereof, those containing basic copper carbonate as a component thereof, those containing copper hydroxide as a component thereof, or those containing copper oxide and manganese oxide as components thereof have been used for cleaning a gas containing a phosphine or a silane gas, the cleaning agents are deactivated through immersion in water or through a similar method to a safe level where the human body and the environment are not adversely affected, and are subsequently treated as industrial wastes. If a copper component and a manganese component can be recovered from the industrial wastes and recycled as components of a cleaning agent for a harmful gas, not only effective use of resources but also protection of the environment could be attained.
However, nothing has been elucidated about the state of used cleaning agents which have sorbed a harmful component. In addition, studies have never been conducted on, for example, reactivity of a cleaning agent which has sorbed a harmful component or on possibility of generation of a harmful gas during dissolution in acid or neutralization of the cleaning agent. Thus, there has never been developed a method of recovering a copper component and/or a manganese component from a used cleaning agent and of restoring activity of the components so as to make them reusable.
The present inventors have carried out extensive studies in order to solve the aforementioned problems, and have found that by dissolving, in an acidic solution such as sulfuric acid or nitric acid, a cleaning agent containing copper oxide, a cleaning agent containing basic copper carbonate, a cleaning agent containing copper hydroxide, or a cleaning agent containing copper oxide and manganese oxide, the cleaning agents having been used for cleaning a harmful gas containing a phosphine as a harmful component, a copper component or a manganese component can be readily separated from a phosphorus component which has been sorbed in the cleaning agent during the course of cleaning the harmful gas. The inventors have also found that, by dissolving, in an acidic solution such as sulfuric acid or nitric acid, a cleaning agent containing basic copper carbonate, a cleaning agent containing copper hydroxide, or a cleaning agent containing copper oxide and manganese oxide, the cleaning agents having been used for cleaning a harmful gas containing a silane gas as a harmful component, a copper component or a manganese component can be readily separated from a silicon component which has been sorbed in the cleaning agent during the course of cleaning the harmful gas. The present invention has been accomplished on the basis of these findings.
Thus, an object of the present invention is to provide a method of effectively recovering a copper component or a manganese component, in a recyclable form, from a cleaning agent containing copper oxide, a cleaning agent containing basic copper carbonate, a cleaning agent containing copper hydroxide, or a cleaning agent containing copper oxide and manganese oxide which has been used for removing a phosphine or a silane gas contained in a discharge gas produced during the course of a semiconductor production step or a similar step.
Accordingly, the present invention provides a method of recovering a cleaning agent, the cleaning agent having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas, and being at least one species selected from among a cleaning agent containing copper oxide as a component thereof, a cleaning agent containing basic copper carbonate as a component thereof, and a cleaning agent containing copper hydroxide as a component thereof, the method comprising:
immersing the cleaning agent in an acidic solution, to thereby dissolve the cleaning agent;
adding to the resultant solution a precipitant for copper, to thereby cause a copper compound to precipitate;
separating a copper component from a phosphorus component which has been sorbed in the cleaning agent during the course of cleaning the harmful gas; and
recovering the copper component of the cleaning agent.
The present invention also provides a method of recovering a cleaning agent, the cleaning agent having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas, and being at least one species selected from among a cleaning agent containing copper oxide as a component thereof, a cleaning agent containing basic copper carbonate as a component thereof, and a cleaning agent containing copper hydroxide as a component thereof, the method comprising:
immersing the cleaning agent in an acidic solution, to thereby dissolve the cleaning agent;
adding to the resultant solution a precipitant for phosphorus, to thereby cause a phosphorus compound to precipitate;
separating a phosphorus component which has been sorbed in the cleaning agent during the course of cleaning the harmful gas from a copper component;
adding a precipitant for copper to the solution from which the phosphorus component has been removed, to thereby cause a copper compound to precipitate; and
recovering the copper component of the cleaning agent.
The present invention also provides a method of recovering a cleaning agent, the cleaning agent having been used for removing, through contact with a harmful gas, a silane gas contained as a harmful component in the harmful gas, and being at least one species selected from a cleaning agent containing basic copper carbonate as a component thereof and a cleaning agent containing copper hydroxide as a component thereof, the method comprising:
immersing the cleaning agent in an acidic solution, to thereby transform a copper component to a soluble copper salt and cause a silicon component to precipitate in the form of silicon oxide, the silicon component having been sorbed in the cleaning agent during the course of cleaning the harmful gas;
separating the silicon component from the copper component;
adding a precipitant for copper to the solution from which the silicon component has been removed, to thereby cause a copper compound to precipitate; and
recovering the copper component of the cleaning agent.
The present invention also provides a method of recovering a cleaning agent, the cleaning agent having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas, and containing copper oxide and manganese oxide as components thereof, the method comprising:
immersing the cleaning agent in an acidic solution, to thereby dissolve the cleaning agent;
adding to the resultant solution a precipitant for copper and manganese, to thereby cause a copper compound and a manganese compound to precipitate;
separating a copper component and a manganese component from a phosphorus component which has been sorbed in the cleaning agent during the course of cleaning the harmful gas; and
recovering the copper component and the manganese component of the cleaning agent.
The present invention also provides a method of recovering a cleaning agent, the cleaning agent having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas, and containing copper oxide and manganese oxide as components thereof, the method comprising:
immersing the cleaning agent in an acidic solution, to thereby dissolve the cleaning agent;
adding to the resultant solution a precipitant for phosphorus, to thereby cause a phosphorus compound to precipitate;
separating a phosphorus component which has been sorbed in the cleaning agent during the course of cleaning the harmful gas, from a copper component and a manganese component;
adding a precipitant for copper and manganese to the solution from which the phosphorus component has been removed, to thereby cause a copper compound and a manganese compound to precipitate; and
recovering the copper component and the manganese component of the cleaning agent.
The present invention also provides a method of recovering a cleaning agent, the cleaning agent having been used for removing, through contact with a harmful gas, a silane gas contained as a harmful component in the harmful gas, and containing copper oxide and manganese oxide as components thereof, the method comprising:
immersing the cleaning agent in an acidic solution, to thereby transform a copper component and a manganese component to a soluble copper salt and a soluble manganese salt, respectively, and cause a silicon component to precipitate in the form of silicon oxide, the silicon component having been sorbed in the cleaning agent during the course of cleaning the harmful gas;
separating the silicon component from the copper component and the manganese component;
adding a precipitant for copper and manganese to the solution from which the silicon component has been removed, to thereby cause a copper compound and a manganese compound to precipitate; and
recovering the copper component and the manganese compound of the cleaning agent.
Numerous modifications and variations of the present invention are possible in light of the spirit of the present invention, and are not to be excluded from the scope of the present invention.
The method of the present invention for recovering a cleaning agent is applied to a method of recovering a copper component and/or a manganese component from a cleaning agent containing copper oxide, a cleaning agent containing basic copper carbonate, a cleaning agent containing copper hydroxide, or a cleaning agent containing copper oxide and manganese oxide, the cleaning agents having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas. The method of the present invention for recovering a cleaning agent is also applied to a method of recovering a copper component or a manganese component from a cleaning agent containing basic copper carbonate, a cleaning agent containing copper hydroxide, or a cleaning agent containing copper oxide and manganese oxide, the cleaning agents having been used for removing, through contact with a harmful gas, a silane gas contained as a harmful component in the harmful gas.
The method of the present invention is drawn to a method of recovering a cleaning agent, the cleaning agent having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas, and being a cleaning agent containing copper oxide as a component thereof, a cleaning agent containing basic copper carbonate as a component thereof, or a cleaning agent containing copper hydroxide as a component thereof, the method comprising: immersing the cleaning agent in As an acidic solution, to thereby dissolve the cleaning agent; adding to the resultant solution a precipitant for copper or a precipitant for phosphorus, to thereby cause a copper compound or a phosphorus compound to precipitate; separating a phosphorus component which has been sorbed in the cleaning agent during the course of cleaning the harmful gas from a copper component; and recovering the copper component of the cleaning agent.
The method of the present invention is drawn to a method of recovering a cleaning agent, the cleaning agent having been used for removing, through contact with a harmful gas, a silane gas contained as a harmful component in the harmful gas, and being a cleaning agent containing basic copper carbonate as a component thereof or a cleaning agent containing copper hydroxide as a component thereof, the method comprising: immersing the cleaning agent in an acidic solution, to thereby transform a copper component to a soluble copper salt and cause a silicon component to precipitate in the form of silicon oxide, the silicon component having been sorbed in the cleaning agent during the course of cleaning the harmful gas; separating the silicon component from the copper component; adding a precipitant for copper to the solution from which the silicon component has been removed, to thereby cause a copper compound to precipitate; and recovering the copper component of the cleaning agent.
The method of the present invention is drawn to a method of recovering a cleaning agent, the cleaning agent having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas, and containing copper oxide and manganese oxide as components thereof, the method comprising: immersing the cleaning agent in an acidic solution, to thereby dissolve the cleaning agent; adding to the resultant solution a precipitant for copper and manganese or a precipitant for phosphorus, to thereby cause either a copper compound and a manganese compound or a phosphorus compound to precipitate; separating a phosphorus component which has been sorbed in the cleaning agent during the course of cleaning the harmful gas from a copper component and a manganese component; and recovering the copper component and the manganese component of the cleaning agent.
The method of the present invention is drawn to a method of recovering a cleaning agent, the cleaning agent having been used for removing, through contact with a harmful gas, a silane gas contained as a harmful component in the harmful gas, and containing copper oxide and manganese oxide as components thereof, the method comprising: immersing the cleaning agent in an acidic solution, to thereby transform a copper component and a manganese component to a soluble copper salt and a soluble manganese salt, respectively, and cause a silicon component to precipitate in the form of silicon oxide, the silicon component having been sorbed in the cleaning agent during the course of cleaning the harmful gas; separating the silicon component from the copper component and the manganese component; and recovering the copper component and the manganese compound of the cleaning agent.
The harmful gas to which the method of the present invention is to be applied is a gas containing as a harmful component at least a phosphine and/or a silane gas, such as silane or disilane. The base gas of the harmful gas is typically a gas such as nitrogen, argon, helium, or hydrogen. In the present invention, the phosphine serving as a harmful component includes phosphine, diphosphine, and alkylphosphines such as monomethylphosphine and t-butylphosphine, and the silane gas includes silane, disilane, and silicon halogenides such as monochlorosilane and dichlorosilane.
In the present invention, before use, the cleaning agent contains as a component thereof at least copper oxide, basic copper carbonate, copper hydroxide, or copper oxide and manganese oxide.
The cleaning agent containing copper oxide as a component thereof may contain, in addition to copper oxide, at least one metal selected from lithium, sodium, potassium, magnesium, calcium, strontium, barium, titanium, zirconium, lanthanum, vanadium, niobium, tantalum, molybdenum, tungsten, iron, cobalt, nickel, zinc, aluminum, silicon, tin, lead, antimony, bismuth, and copper, and/or at least one oxide of these metal other than copper oxide.
The cleaning agent containing basic copper carbonate or copper hydroxide as a component thereof may contain, in addition to basic copper carbonate or copper hydroxide, at least one metal selected from lithium, sodium, potassium, magnesium, calcium, strontium, barium, titanium, zirconium, lanthanum, vanadium, niobium, tantalum, molybdenum, tungsten, iron, cobalt, nickel, zinc, aluminum, silicon, tin, lead, antimony, bismuth, and copper, and/or at least one oxide of these metal.
The cleaning agent containing copper oxide and manganese oxide as components thereof may contain, in addition to copper oxide and manganese oxide, at least one metal selected from lithium, sodium, potassium, magnesium, calcium, strontium, barium, titanium, zirconium, lanthanum, vanadium, niobium, tantalum, molybdenum, tungsten, iron, cobalt, nickel, silver, platinum, ruthenium, palladium, zinc, aluminum, silicon, tin, lead, antimony, bismuth, copper, and manganese, and/or at least one metallic compound other than copper oxide and manganese oxide.
Even when the cleaning agent to be treated in the present invention contains the above-described metal, metal oxide, or metal compound, the cleaning agent typically contains, before use, copper oxide, basic copper carbonate, copper hydroxide, and/or copper oxide and manganese oxide in a total amount of 70 wt. % or more.
In the present invention, the cleaning agent from which the component is to be recovered includes the aforementioned cleaning agents; i.e., a cleaning agent containing copper oxide as a component thereof, a cleaning agent containing basic copper carbonate as a component thereof, a cleaning agent containing copper hydroxide as a component thereof, and a cleaning agent containing copper oxide and manganese oxide as components thereof, the agents having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas; and a cleaning agent containing basic copper carbonate as a component thereof, a cleaning agent containing copper hydroxide as a component thereof, and a cleaning agent containing copper oxide and manganese oxide as components thereof, the cleaning agents having been used for removing, through contact with a harmful gas, a silane gas contained as a harmful component in the harmful gas.
According to the method of recovering a cleaning agent of the present invention, a copper component or a manganese component can be recovered, as a highly valuable component of a cleaning agent having cleaning performance virtually equivalent to that of the unused agent, from a cleaning agent containing as a component(s) copper oxide, basic copper carbonate, copper hydroxide, or copper oxide and manganese oxide, the cleaning agents having been used for cleaning a harmful gas. Examples of the highly valuable component include copper oxide, basic copper carbonate, and copper hydroxide, each having a BET specific surface area of 10 m2/g or more, and manganese oxide having a BET specific surface area of 50 m2/g or more. From these recovered components, a cleaning agent having a BET specific surface area of 10 m2/g or more can be prepared. Furthermore, according to the method of recovering a cleaning agent of the present invention, there can be recovered copper oxide, basic copper carbonate, or copper hydroxide, each having a BET specific surface area of 50 m2/g or more, or manganese oxide having a BET specific surface area of 150 m2/g or more. From the above recovered components, a cleaning agent having a BET specific surface area of 50 m2/g or more can be prepared.
There will next be described in detail the method of recovering a copper component from a cleaning agent containing copper oxide, a cleaning agent containing basic copper carbonate, or a cleaning agent containing copper hydroxide, the agents having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas.
The cleaning agent containing copper oxide, the cleaning agent containing basic copper carbonate, or the cleaning agent containing copper hydroxide, the cleaning agents having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas, is removed from a cleaning column, and then immersed in an acidic solution, to thereby dissolve in the solution. Examples of the acidic solution to be used for dissolving the cleaning agent include inorganic acids such as sulfuric acid, nitric acid, and hydrochloric acid, and organic acids such as formic acid and acetic acid. Of these, sulfuric acid, nitric acid, and hydrochloric acid are preferred, in that these acids can readily dissolve the used cleaning agent.
The concentration of the acidic solution and the amount of the solution to the cleaning agent are not particularly limited, and vary in accordance with conditions such as the type of the cleaning agent and the type of the acidic solution. However, the acidic solution can be used under conditions such that soluble components of the cleaning agent can readily dissolved. In the case in which sulfuric acid, nitric acid, or hydrochloric acid is used, the concentration is not particularly limited. The concentration is preferably 5-30 wt. %, and the amount of the acidic solution based on 1 kg of the cleaning agent is typically approximately 1-25 kg, preferably approximately 4-12 kg. The temperature upon immersion of the cleaning agent in the acidic solution for dissolution is typically 100xc2x0 C. or lower, preferably 30-80xc2x0 C.
To the acidic solution in which the aforementioned cleaning agent has been dissolved, a precipitant for copper or a precipitant for phosphorus is added, to thereby cause a copper compound or a phosphorus compound to precipitate. Examples of the precipitant for copper include lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, and ammonium hydrogencarbonate. Examples of the precipitant for phosphorus include magnesium chloride, calcium chloride, magnesium sulfate, magnesium nitrate, and calcium nitrate.
As described above, the copper component can be separated from the phosphorus component. When the copper component is separated through precipitation of a phosphorus compound, the copper component remains dissolved in the solution, and therefore, a precipitant for copper must be added. In either case, the copper component can be precipitated in the form of basic copper carbonate or copper hydroxide by, for example, adjusting pH during precipitation. The thus-yielded precipitate is washed with water and dried, to thereby recover the copper component in the form of basic copper carbonate or copper hydroxide. Alternatively, after the precipitate has been washed with water and dried, the dried product is calcined, to thereby recover the copper component in the form of copper oxide. The basic copper carbonate, copper hydroxide, or copper oxide which is recovered in the aforementioned manner can be provided with a BET specific surface area equal to that of the unused cleaning agent. In the method of the present invention for recovering a cleaning agent, the component to be recovered is not limited to a copper component, but may also include other metallic components in combination with the copper component.
There will next be described in detail the method of recovering a copper component from a cleaning agent containing basic copper carbonate or a cleaning agent containing copper hydroxide, the agents having been used for removing, through contact with a harmful gas, a silane gas contained as a harmful component in the harmful gas.
In a manner similar to that described above, the cleaning agent containing basic copper carbonate or the cleaning agent containing copper hydroxide, the cleaning agents having been used for cleaning a harmful gas containing a silane gas as a harmful component, is removed from a cleaning column, and then immersed in an acidic solution. When the used cleaning agent is immersed in an acidic solution, the copper component contained in the cleaning agent is dissolved in the acidic solution, to thereby transform into a soluble copper salt, and a silicon component which has been sorbed in the cleaning agent during the course of a cleaning process is precipitated in the form of silicon oxide.
Examples of the acidic solution to be used for dissolving the cleaning agent include inorganic acids such as sulfuric acid, nitric acid, and hydrochloric acid, and organic acids such as formic acid and acetic acid. Of these, sulfuric acid, nitric acid, and hydrochloric acid are preferred, for the same reason as described above. The concentration of the acidic solution and the amount of the solution to be added to the cleaning agent are adjusted in a manner similar to that of the aforementioned case. For example, in the case in which sulfuric acid, nitric acid, or hydrochloric acid is used, the concentration is preferably 5-30 wt. %, and the amount of the acidic solution based on 1 kg of the cleaning agent is typically approximately 1-25 kg, preferably approximately 4-12 kg. The temperature upon immersion of the cleaning agent in the acidic solution for dissolution is typically 100xc2x0 C. or lower, preferably 30-80xc2x0 C.
Upon or after immersion of the used cleaning agent, hydrogen peroxide may also be added to the acidic solution, to thereby promote solidification of silicon.
To the solution containing a copper component from which solution the silicon component has been removed in the aforementioned manner, a precipitant for copper is added. Examples of the precipitant for copper include lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, and ammonium hydrogencarbonate. During precipitation, by, for example, adjusting pH, the copper component can be precipitated in the form of basic copper carbonate or copper hydroxide. The thus-yielded precipitate is washed with water and dried, to thereby recover the copper component in the form of basic copper carbonate or copper hydroxide. Alternatively, after the precipitate has been washed with water and dried, the dried product is calcined, to thereby recover the copper component in the form of copper oxide. The basic copper carbonate, copper hydroxide, or copper oxide which is recovered in the aforementioned manner can be provided with a BET specific surface area equal to that of the unused cleaning agent to be used for cleaning a harmful gas containing a silane gas. In the method of the present invention for recovering a cleaning agent, the component to be recovered is not limited to a copper component, but may also include other metallic components in combination with the copper component.
There will next be described in detail the method of recovering a copper component and a manganese component from a cleaning agent containing copper oxide and manganese oxide, the cleaning agent having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas.
In a manner similar to that described above, the cleaning agent containing copper oxide and manganese oxide, the cleaning agent having been used for cleaning a harmful gas containing a phosphine as a harmful component, is removed from a cleaning column, and then immersed in an acidic solution, to thereby dissolve in the solution. Examples of the acidic solution to be used for dissolving the cleaning agent include inorganic acids such as sulfuric acid, nitric acid, and hydrochloric acid, and organic acids such as formic acid and acetic acid. Of these, sulfuric acid, nitric acid, and hydrochloric acid are preferred, for the same reason as described above.
The concentration of the acidic solution, the amount of the solution to be added to the cleaning agent, and the temperature upon immersion of the cleaning agent in the acidic solution are adjusted in a manner similar to that of the aforementioned case. Since manganese is somewhat difficult to dissolve in an acidic solution, a reducing agent is preferably added to the solution, upon or after immersion of the cleaning agent in the solution, to thereby enhance solubility of manganese in the solution. Examples of the reducing agent include hydrogen peroxide, formic acid, acetic acid, and sulfurous acid.
To the acidic solution in which the cleaning agent has been dissolved in a previously mentioned manner, a precipitant for copper and manganese or a precipitant for phosphorus is added, to thereby cause either a copper component and a manganese component or a phosphorus compound to precipitate in the form of copper compound and manganese compound or phosphorus compound. Thus, the copper component and the manganese component are isolated from the phosphorus component. Precipitants similar to those employed for copper can be used as precipitants for copper and manganese.
As described above, the copper component and the manganese component can be separated from the phosphorus component. When the copper component and the manganese component are separated through precipitation of a phosphorus compound, the copper component and the manganese component remain dissolved in the solution, and therefore, a precipitant for copper and manganese must be added. In either case, the copper component and the manganese component can both be precipitated in the form of basic copper carbonate and manganese carbonate by, for example, adjusting pH during precipitation. The thus-yielded precipitate is washed with water, dried, and calcined, to thereby recover the copper component and the manganese component in the form of a mixture of copper oxide and manganese oxide. The copper oxide and manganese oxide which are recovered in the aforementioned manner can be provided with a BET specific surface area equal to that of the unused cleaning agent. In the method of the present invention for recovering a cleaning agent, the component to be recovered is not limited to a copper component and a manganese component, but may also include other metallic components in combination with the copper component and the manganese compound.
There will next be described in detail the method of recovering a copper component and a manganese component from a cleaning agent containing copper oxide and manganese oxide, the cleaning agent having been used for removing, through contact with a harmful gas, a silane gas contained as a harmful component in the harmful gas.
In a manner similar to that described above, the cleaning agent containing copper oxide and manganese oxide, the cleaning agent having been used for cleaning a harmful gas containing a silane gas as a harmful component, is removed from a cleaning column, and then immersed in an acidic solution. Examples of the acidic solution to be used for dissolving the cleaning agent include inorganic acids such as sulfuric acid, nitric acid, and hydrochloric acid, and organic acids such as formic acid and acetic acid. Of these, sulfuric acid, nitric acid, and hydrochloric acid are preferred, for the same reason as described above.
The concentration of the acidic solution, the amount of the solution to be added to the cleaning agent, and the temperature upon immersion of the cleaning agent in the acidic solution are adjusted in a manner similar to that of the aforementioned case. Since manganese is somewhat difficult to dissolve in an acidic solution, a reducing agent is preferably added to the solution, upon or after immersion of the cleaning agent in the solution, to thereby enhance solubility of manganese in the solution. Examples of the reducing agent include hydrogen peroxide, formic acid, acetic acid, and sulfurous acid. Of these, hydrogen peroxide is preferred, in that hydrogen peroxide can promote solidification of silicon as well as solubility of manganese in an acidic solution.
By immersing the cleaning agent in the acidic solution, copper and manganese form a soluble copper salt and a soluble manganese salt, respectively, while silicon which has been sorbed in the cleaning agent during the course of cleaning the harmful gas is precipitated in the form of silicon oxide.
To the solution containing a copper component and a manganese component, the silicon component having been removed from the solution in the aforementioned manner, a precipitant for copper and manganese is added, to thereby cause a copper compound and a manganese compound to precipitate. Examples of the precipitant for copper and manganese include lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, and ammonium hydrogencarbonate. During precipitation, by, for example, adjusting pH, the copper component and the manganese component can be precipitated in the form of basic copper carbonate and manganese carbonate, respectively. The thus-yielded precipitate is washed with water, dried, and calcined, to thereby recover the copper component and the manganese component in the form of a mixture of copper oxide and manganese oxide. The copper oxide and manganese oxide which are recovered in the aforementioned manner can be provided with a BET specific surface area equal to that of the unused cleaning agent. In the method of the present invention for recovering a cleaning agent, the component to be recovered is not limited to a copper component and a manganese component, but may also include other metallic components in combination with the copper component and the manganese component.
According to the method of the present invention for recovering a cleaning agent, a copper component or a manganese component can be effectively recovered, in a recyclable form, from a cleaning agent containing copper oxide as a component thereof, a cleaning agent containing basic copper carbonate as a component thereof, a cleaning agent containing copper hydroxide as a component thereof, or a cleaning agent containing copper oxide and manganese oxide as components thereof, the cleaning agents having been used for removing a phosphine contained in a discharge gas produced during a semiconductor production step or a similar step. Also, a copper component or a manganese component can be effectively recovered, in a recyclable form, from a cleaning agent containing basic copper carbonate as a component thereof, a cleaning agent containing copper hydroxide as a component thereof, or a cleaning agent containing copper oxide and manganese oxide as components thereof, the cleaning agents having been used for removing a silane gas contained in a discharge gas produced during a semiconductor production step or a similar step.
The present invention will next be described in more detail by way of examples, which should not be construed as limiting the invention thereto.